Copper is increasing being used as the metal component of metalized layers of semiconductor structures due to its higher conductivity and correspondingly increased efficiency in signal transmission compared to many other metals. Cap layers are being evaluated over copper-containing metallization layers to protect copper from oxidation, to improve adhesion to overlying layers and to decrease electromigration. Ru is one of the candidate materials as a cap layer or a component of a cap layer for such purposes.
A metalized layer is formed of a dielectric layer having a pattern of trenches and/or vias formed therein. The trenches and/or vias are filled in with a copper-containing material using the damascene or dual-damascene technique. Ru can be selectively deposited on the surface of the copper-containing material using chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD) and other deposition techniques.
As semiconductor structures are scaled down, the area of individual copper-containing metal lines decreases. Such decreased area increase the difficulty of depositing Ru on the surface copper-containing material filling the vias and/or trenches formed in the dielectric layer.